Effect of Wind Velocity on Heat Losses

In contrast to its effect on bare surfaces, wind velocity has little effect on heat losses from well-insulated equipment. This small increase in heat loss from well-insulated equipment is explained by the fact that wind velocity increases the conductance from the surface to the air, but not the conductance through the insulation. If the insulation is not sealed properly and there is air movement through the insulation, the heat loss is increased considerably. It is estimated for design purposes that, from a well-sealed insulation in a wind velocity of 25 mph, the heat loss increases 30 percent for 1-inch insulation, 20 percent for 2-inch insulation and 10 percent for 3-inch insulation. If no insulation is applied, or if the insulation is sealed improperly, the heat loss (in a wind velocity of 25 mph) is increased over that in still air conditions by two to four times. The heat loss calculations should be based on the effective minimum temperature resulting from the wind speed as shown in the wind chill chart.